Ashlee Simpson claimed a chronic gastric disorder was the cause of her lip-synching miscue on "Saturday Night Live" this past weekend. The singer said that acid reflux disease caused her to lose her voice and rely on a backing tape for her performance.

"It's so embarrassing," Simpson said when she called in to "TRL" Monday (October 25), "because it sucks. The total situation was a bummer. I made a complete fool of myself."

Simpson said she suffers from a chronic condition of "severe" acid reflux disease — a condition in which the stomach's liquid content regurgitates into the esophagus — and that it began acting up at around 6 p.m. on Saturday, causing her to "completely [lose] my voice." Her doctor advised her not sing, stating that she would damage her voice, and her father and manager, Joe Simpson, insisted she take it easy by using a backing track, a common (if seldom acknowledged) concert aid that allows singers to either lip-synch to, or sing along with, a guide-vocal track. "My dad was like, 'I'm sorry, you have to sing along with the backing track,' " Simpson said Monday.

Though Simpson's first performance in the show — her hit "Pieces of Me" — went off without a hitch, the second, "Autobiography," was derailed when a pre-recorded track of her voice (singing "Pieces of Me") began playing while Simpson was holding her mic to the side and had her mouth closed. When the track came on, Simpson tried to dance a little jig instead, but after about 30 seconds, she exited the stage as her band continued performing. The show cut to a commercial.

At the end of the show, host Jude Law tried to help Simpson brush the moment aside by shrugging, "What can I say, folks? Live TV." For her part, Simpson initially placed the blame on her band. "I feel so bad," she told the audience. "My band started playing the wrong song. And I didn't know what to do, so I thought I'd do a hoe-down. I'm sorry. It's live TV. Things happen. I'm sorry."

Joe Simpson told Los Angeles radio station KIIS-FM, "Just like any artist in America, she has a backing track that she pushes so you don't have to hear her croak through a song on national television. No one wants to hear that. Every artist that I know in this business has had vocal problems at some time, from Celine [Dion] on down. So you've got to do what you've got to do."

Ashlee said that she wasn't happy with the decision to use a backing track, and emphasized that it's not something she normally relies upon. She's performed live on television on previous occasions, including MTV News' pre-show to the Video Music Awards, "By the Shore," and the Teen Choice Awards. And in fact, Simpson had rehearsed "Autobiography" live on Thursday (see "Ashlee Simpson Preparing To Take On Tara Reid").

"I was so upset," she said, "because I have never done that before. But my voice wasn't strong enough. I couldn't even speak."

During the show, a further mishap made the backing track obvious to everyone when, according to her record label, a "computer glitch" triggered "a cut from her album" to play instead of a drum cue. Simpson placed the blame a little more squarely on her drummer, saying he was the one who "pressed the wrong button."

"I didn't know what to do," she said. "I just froze. My band kept playing the song, like they were always told [to do]. We all went into a state of shock. 'Omigod, what do I do?' So I did the hoe-down and then I ran off."

Simpson has since been widely attacked for the snafu, with an interview she gave to Lucky magazine coming back to haunt her. When asked what her take on lip-synching was, she had told the magazine, "I'm totally against it and offended by it. I'm going to let my real talent show, not just stand there and dance around. Personally, I'd never lip-synch. It's just not me."

Simpson's official Web site has been flooded with more than 12,000 posts, many of them negative. Initially, it appeared that Simpson was responding to the posts — blaming her hectic work schedule for wearing down her voice — but a spokesperson has since claimed that the posts were not written by the singer.

To make sure a similar snafu doesn't happen again when she performs live on Monday for the Radio Music Awards in Las Vegas, Simpson said she got a cortisone shot in her lower back "and I'm much better."

"I hope I get a chance [to return to 'SNL']," she added. "My voice is so much better now. Sorry about that."

The Radio Music Awards in Las Vegas are to be broadcast live on NBC at 9 p.m.